1. Field
The present invention relates to an apparatus and method for extracting oils and fats with the use of a solvent. More particularly, the present invention relates to extracting oils and fats from oil-bearing substances without exposing the substances, oils, or fats to degrading temperatures.
2. Related Art
Most materials, whether synthetic or naturally occurring, contain some amount of oils and fats. These oils and fats, when extracted from the material, often have useful properties that can be utilized for a range of purposes. For example, oil extracted from corn may be used for cooking or as a source of biodiesel, while the fat extracted from various naturally occurring substances may be used in cosmetics such as lipstick.
Various solvents may be used to extract oils and fats from oil-bearing substances. Some processes use carbon dioxide in a super critical phase for extraction of oils from various natural products. However, due to the expense of carbon dioxide extraction, it is typically only used for expensive items or in high volume production, such as pharmaceuticals and instant coffee.
Other commonly used solvents for oil extraction are hydrocarbons such as butane, isobutane, and propane, for example, as described in U.S. Pat. Nos. 1,802,533; 2,254,245; 5,1041,245; 5,980,964; and 6,225,483.
In the extraction processes described in the aforementioned publications, raw material is bathed or wetted with solvent for a sufficiently long time to allow the oils and fats to dissolve in the solvent, or to form a miscella floating on the solvent, the solvent subsequently being removed by heating and/or by means of a vacuum to boil off the solvent. The heating of the extracted solvent and oil mixture is disadvantageous since it destroys some of the qualities of the extracted oil, affecting for example its flavor, olfactory profile, vitamin content, and other heat-sensitive components.
Extraction processes as described in U.S. Pat. Nos. 2,254,245; 5,980,964; and 6,225,483 suggest the use of cold solvents for extraction. The cold solvent however, or raw material, is chilled by a cooling system, which is energy intensive and therefore fairly costly to operate.
A further disadvantage of known extraction processes is that they use large quantities of solvent. Process times are relatively high because of the need to bathe the raw material in the solvent for a lengthy period of time, compounded by the need to subsequently remove the solvent from the extracted oils and fats. It is also difficult with known extraction methods to obtain very high yields of oils from raw materials without multiple extraction passes. Besides the time and expense, subjecting material to multiple extraction runs adversely affects the qualities of the extracted oil, the yield, and the olfactory profile of the oils. This is undesirable particularly for any substance with low oil content that is considered to be relatively rare.
One known extraction process described in U.S. Pat. No. 7,002,029 uses adiabatic cooling to extract oils from raw materials using a minimal amount of solvent. However, this process has the disadvantage of significantly cooling the material, which may alter the properties of the material and its oil or fat. Additionally, this can cause material to freeze-up in the oil-collecting chamber during the extraction process.
Accordingly, there is a need for an improved extraction of oil and fats from oil-bearing substances that does not suffer from the problems and limitations of the prior art.